It is desirable in transistors to be able to drive high currents. Driving high currents can enhance a transistor's operating performance including its operating speed. In field effect transistors (FETs), current flow is primarily conducted by way of the drain-to-source current Ids. While higher drive currents can be achieved by building wider FET devices, tradeoffs are made in valuable wafer real estate. Larger devices also typically have larger capacitances which can adversely impact device performance. Also typically, a high Ids current in FET devices can result in an increased sub-threshold current leakage. It is desirable in FETs to minimize the sub-threshold current leakage. Accordingly, it is desirable to have the Ids ratio of on-state current (Ion) to off-state current (Ioff) be as high as possible. Such improves sub-threshold device leakage characteristics as well as increases the transistor's operating speed performance.
This invention arose out of concerns associated with improving field effect transistor performance.